Move withRoot from JS to TS

lib/withRoot.jsx → lib/withRoot.tsx

 import CssBaseline from "@material-ui/core/CssBaseline";
 import { MuiThemeProvider } from "@material-ui/core/styles/";
-import PropTypes from "prop-types";
 import React from "react";
 
 import createPageContext from "./createPageContext";
@@ -8,7 +7,12 @@ import getPageContext from "./getPageContext";
 
 function withRoot(Component) {
   let pageContext = null;
-  class WithRoot extends React.Component {
+
+  interface Props {
+    pageContext: any;
+  }
+
+  class WithRoot extends React.Component<Props> {
     constructor(props, context) {
       super(props, context);
 
@@ -16,12 +20,20 @@ function withRoot(Component) {
       pageContext = propsPageContext || getPageContext(process.browser, createPageContext);
     }
 
+    static getInitialProps = (ctx) => {
+      if (Component.getInitialProps) {
+        return Component.getInitialProps(ctx);
+      }
+
+      return {};
+    };
+
     render() {
       // MuiThemeProvider makes the theme available down the React tree thanks to React
       // context.
       return (
         <MuiThemeProvider
-          theme={pageContext.theme}>
+          theme={(pageContext as any).theme}>
           {/* CssBaseline kickstart an elegant, consistent, and simple baseline to */}
           {/* build upon. */}
           <CssBaseline />
@@ -31,22 +43,6 @@ function withRoot(Component) {
     }
   }
 
-  WithRoot.defaultProps = {
-    pageContext: null,
-  };
-
-  WithRoot.propTypes = {
-    pageContext: PropTypes.shape(),
-  };
-
-  WithRoot.getInitialProps = (ctx) => {
-    if (Component.getInitialProps) {
-      return Component.getInitialProps(ctx);
-    }
-
-    return {};
-  };
-
   return WithRoot;
 }